In physics class, the girl to boy ratio is $6$ to $7$. If there are a total of $52$ students, how many girls are there?
Solution: A ratio of $6$ girls to $7$ boys means that a set of $13$ students will have $6$ girls and $7$ boys. A class of $52$ students has $4$ sets of $13$ students. Because we know that there are $6$ girls in each set of $13$ students, the class must have $4$ groups of $6$ girls each. There is a total of $24$ girls in physics class.